1. Field of the Invention
The present invention relates to a tensioner including a tensioner body having a plunger bore whose one end is open, a cylindrical plunger slidably inserted into the plunger bore, and biasing means for urging the plunger outward, the tensioner being fixed to a wall surface that has an oil discharge hole.
2. Description of the Related Art
Regarding existing types of tensioner that have been widely used in a transmission device incorporated in a timing system or the like of an engine, a tensioner is used to apply appropriate tension to the slack side of a transmission belt or a transmission chain and reduce vibration during the drive. A tensioner is well known, which includes a tensioner body having a plunger bore whose one end is open, a cylindrical plunger slidably inserted into the plunger bore, and biasing means for urging the plunger outward, and which is fixed to a wall surface that has an oil discharge hole, moreover in which pressurized oil is supplied from the oil discharge hole, thereby achieving hydraulic damping effect, hydraulic drive force, and oil lubricating effect.
In such a tensioner, when the engine or the like is stopped and the pressurized oil is no longer supplied, the oil then flows out through a gap between the plunger bore and the plunger, or from an oil supply hole or the like that connects the plunger bore with the outside of the tensioner body, hence the oil remaining inside the tensioner is reduced.
When the engine is restarted in such a state, there is a time lag until the pressurized oil starts to be supplied again, so that rattling and clattering tend to occur because of the lack of hydraulic drive force and insufficient hydraulic damping effect. Also, sliding parts can readily be damaged due to reduced lubricating effect of oil.
Therefore, it is necessary to ensure that a sufficient amount of oil remains inside the tensioner during the period when there is no supply of pressurized oil.
Known structures that address these issues include a structure that allows additional oil to be stored outside the plunger bore, as shown in Japanese Patent Application Laid-open No. 2013-249939, for example, or a structure that can store an increased amount of oil in the plunger bore and inside the plunger, as shown in Japanese Patent Application Laid-open No. 2014-77465 or No. 2014-134263.